Baboons represent an invaluable source of xenogeneic organ donors for human patients, needed to relieve the great lack of available human donor organs. However, the risk of transmitting or allowing establishment of a zoonotic virus in humans is a real, and frightening consideration. Baboons are host to a number of known viruses. This study will focus on cytomegalovirus since this is the most commonly transmitted virus in human transplantation procedures and is a major cause of many problems in immunosuppressed transplant recipients. This project will identify the indigenous CMV of baboons (BaCMV) and develop sensitive diagnostic assays. These tests will be capable of detecting BaCMV-infected potential organ donors, and useful in the screening of baboons for the establishment of specific pathogen free breeding colonies. Reagents developed in this project will also allow detection (and differentiation from HCMV) of BaCMV infection in human transplant recipients. The first goal in this project is the isolation of an indigenous CMV from baboons. This virus isolate (s) will be preliminarily characterized and used in a first generation diagnostic ELISA to detect BaCMV. This assay will be more sensitive than current detection tests since it will use BaCMV infected cells as a target antigen rather than HCMV infected cells. The most immunoreactive BaCMV proteins, as produced in a genomic X-virus expression library will be identified using CMV-positive baboon sera, cloned and sequenced. These proteins will be produced in bacterial expression systems and used in a series of second generation diagnostic assays. These strong target antigens will make the detection tests even more sensitive. In addition, the conserved CMV genes for glycoprotein B and the major immediate early protein will be cloned, sequenced and this data used to develop PCR assays to allow detection and unequivocal identification of the baboon virus in human transplant recipients.